Horn System Chevrolet Chevy Express G3500

Fastener Tightening Specifications

Fastener Tightening Specifications

Horns Schematics

For horn schematics refer to appropriate System Wiring Diagrams article.

Scheme 1

Scheme 2

Horns Connector End Views

Horn Assembly Connector End Connector Part Information 12052644 2-Way F Metri-Pack 150 Series- Sealed (L-GY) Pin Wire Color Circuit No. Function A BK 1250 Ground B D-GN 1329 Horn Fuse Supply Voltage

Turn Signal/Multifunction Switch - C1 Connector End Connector Part Information 12064862 8-Way F Metri-Pack 150 Series (BK) Pin Wire Color Circuit No. Function A D-BU/WH 1415 Right Front Turn Signal Switch Signal B PK 739 Ignition 1 Voltage C L-BU/WH 1414 Left Front Turn Signal Switch Signal D-F - - Not Used G TN 28 Horn Relay Control H WH 111 Hazard Switch Signal

Diagnostic Starting Point - Horns

Begin the system diagnosis by reviewing the system Description and Operation. Reviewing the Description and Operation information will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the Description and Operation information will also help you determine if the condition described by the customer is normal operation. Refer to Symptoms - Horns in order to identify the correct procedure for diagnosing the system and where the procedure is located.

Symptoms - Horns

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the horn system. Refer to «Checking Aftermarket Accessories»(/chevrolet/chevy-express-g3500/1996-2012/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__checking-aftermarket-accessories) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Perform the following if a horn buzzes or has a harsh tone: Inspect for debris in the joint where the horn fastens to the vehicle. Test the torque of the horn mounting hardware. The horn mounting hardware should be tightened to a torque of 10 N.m (7 lb ft).

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Horns Always On»(/chevrolet/chevy-express-g3500/1996-2012/remont/horns/#horn-system)
2. «Horns Inoperative»(/chevrolet/chevy-express-g3500/1996-2012/remont/horns/#horn-system)
3. «Horns - Poor Tone»(/chevrolet/chevy-express-g3500/1996-2012/remont/horns/#horn-system__horns-poor-tone)

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 4: Tests if ground is constantly being applied to the horn relay.
2. 6: The horn relay control circuit includes the horn slip ring and the horn switch. The horn slip ring and the horn switch must be tested for a short to ground when testing the relay control circuit.

Horns Always On

The numbers below refer to the step numbers on the diagnostic table.

1. 3: Tests for voltage at the battery positive voltage terminal of the horn relay coil.
2. 5: Tests for voltage at the battery positive voltage terminal of the horn relay switch. The HORN fuse supplies power to the battery positive voltage terminal of the horn relay switch.
3. 12: The horns need maximum current flow to operate properly. A high resistance greater than 0.5 ohms in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Inspect the circuits for faults that would restrict current flow.
4. 14: The horn relay control circuit includes the horn slip ring and the horn switch. The horn slip ring and the horn switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit.

Horns Inoperative

Horns - Poor Tone

Horns - Poor Tone

Removal Procedure

1. Raise and support the hood.
2. Disconnect the electrical connectors from the horn assembly.
3. Remove the nut (2) that retains the horn mounting bracket (1) to the vehicle.
4. Remove the horn assembly from the vehicle.
5. Note the location of the trumpet mouth relative to the mounting bracket.
6. Remove the nut holding the horn to the mounting bracket.
7. Remove the horn from the mounting bracket.

Installation Procedure

1. Install the horn to the mounting bracket.
2. Line up the trumpet mouth in the same direction as the original.
3. Install the nut holding the horn to the mounting bracket. Tighten: Tighten the nut to 10 N.m (90 lb in).
4. Install the horn assembly to the vehicle.
5. Install the nut (2) in order to retain the horn mounting bracket (1) to the vehicle. Tighten: Tighten the nut to 25 N.m (18 lb ft).
6. Connect the electrical connectors to the horn assembly.
7. Close the hood.

System Description

The horn system consists of the following components

1. The HORN fuse
2. The horn relay
3. The horn brush slip ring
4. The horn switch
5. The horns

System Operation

The vehicle horns are activated whenever the horn switch is depressed.

Circuit Operation

Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing the horn switch applies ground to the horn relay control circuit. When the horn relay control circuit is grounded, the horn relay is energized and battery positive voltage is applied to the horns through the horn control circuit. The horns sound as long as ground is applied to the horn relay control circuit.

See also:
• Checking Aftermarket Accessories
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Inflatable Restraint Steering Wheel Module Replacement
• Circuit Testing
• Wiring Repairs
• Symptoms - Horns
• Horns System Description and Operation
• Horns - Poor Tone